The field of surface fasteners, including hook-and-loop and self engaging types, is well established, as evidenced by numerous US and international patents for fasteners and methods of manufacturing since at least the mid 20th century. Improvements in the field have largely focused on developing diverse hook and mushroom designs, arraying fastening elements on a surface, increasing hook density, and methods of manufacturing such fasteners in continuous batches by molding or extrusion techniques. In general, these systems include a plurality of hook-like or mushroom-like fastening elements which extend from a generally contiguous sheet form base, with the individual hooks or mushrooms having undersides spaced away from the base.
Molded hookstrips are now often manufactured in a continuous strip on a rotating mold from which individual hooks are stripped by elastically pulling the undercut ends from the mold (for example Jens et al U.S. Pat. No. 6,258,311). Mushroom fasteners as well as some hook fasteners are typically manufactured by first continuously molding a sheet form base with post forms, then heat forming the post ends into a bulbous shape (for example Provost et al U.S. Pat. No. 6,526,633, Parellada et al U.S. Pat. No. 6,708,378 B2).
Typically, both hook-and-loop and self-engaging mushroom fasteners are manufactured as subsidiary products to be attached to a primary product. Fabric like hookstrips are generally contiguous with a woven base and are typically sewn to clothing or flexible materials. Molded hookstrips, as well as self-engaging mushroom systems, are typically molded integrally with a sheet form base which is then attached to a relatively rigid primary product structure by adhesive, welding, or mechanical means. These attachment methods can be problematical in that adhesives may fail, edge peeling often occurs, and they generally result in a relatively thick assembly. Even recently developed “low profile” systems generally have significant thickness which prevents adjoining components from being joined in a flush juxtaposition and are therefore not suitable for many assembly applications. In addition, attached fasteners can be relatively costly for an end product manufacturer in terms of inventory, assembly time, and potential returns. Other factors such as color matching, material compatibility, durability, and material efficiency of the fastener are drawbacks of attached fasteners for many applications. Applications for such attached fasteners are limited by the necessity of attaching the fastener, assuring adhesion, cost, and the relative thickness of the resultant assembly. Therefore, particularly in assembly processes, other methods of attachment are frequently chosen.
In recent years several patents have been issued regarding methods of integrally molding hook-and-loop type hookstrips as part of a primary product (McVicker U.S. Pat. No. 5,656,226, Harvey U.S. Pat. No. 6,224,364 B1, Murasaki et al U.S. Pat. No. 6,678,924 B2). In many instances such integrally molded surface fasteners would appear to be advantageous to industry. However, because these techniques are based upon forcibly removing hook-shaped elements with “blind” undersides from a mold, they appear to be limiting: necessitating complex manufacturing methods; resulting in compromised hook designs of relative weakness; limiting choice of plastic materials; and requiring relatively long dwell times. All of these factors would appear to increase relative cost as well as limit functionality and potential applications.
A few patents and applications have disclosed double-sided surface fasteners (i.e. Kennedy et al U.S. Pat. No. 6,737,147B2, Shepard et al US 2001/0022012 A1, Dudek et al U.S. Pat. No. 6,449,816 B1) Generally these disclosures include means for attaching independently manufactured hookstrip and loop fastener portions in a back to back configuration, resulting in a relatively thick overall assembly when connected.
In pending U.S. patent application Ser. No. 10/015,087, the present applicant has disclosed a method and apparatuses for producing surface fasteners of the slidingly engaging type by utilizing a set of bypassing/biparting dies. This method, among other attributes, allows fastening elements with effectively “blind” undersides to be precisely and economically manufactured with a relatively simple reciprocating molding machine as an integral part of a primary product, or by a continuous molding machine incorporating a rotating die set.
Several examples of prior art include surface fasteners having undercut fastening elements which extend from a fenestrated base structure. Kayaki U.S. Pat. No. 5,067,210 discloses a device having rows of two directional hook sets formed between contiguous structural rows, so as to have a fenestrated base with hook undersides opposite windows in the base. Pacione U.S. Pat. No. 5,384,462 discloses a carpet tape with a fenestrated base structure and hook like elements which do not appear to be related to individual fenestrations. Allan U.S. Pat. No. 5,555,608 discloses (FIG. 19) a somewhat similar structure having individual hooks arrayed in rows of alternating orientation projecting between rows of contiguous structure. In his U.S. Pat. No. 5,640,744, Allan also discloses a fenestrated fastening portion with rib like fastening elements of a similar profile which appears to be double sided. Akeno U.S. Pat. No. 5,797,170 discloses a “mushroom type” fastener wherein individual undersides of each multi-sided fastening element is configured opposite an opening in the fenestrated base structure. Although these examples disclose surface fasteners which appear to be moldable with a byparting die set, their utility seems limited. In each case, the “window” through the base structure is relatively small in relationship to the size of the undercut or “hook” element, which is generally equal to or only slightly larger than the corresponding undercut area. Therefore, hook (or mushroom) density is limited by the number of mold cavities which can reasonably be arrayed in a unit of area because projecting (male) die elements of relatively small dimension would be expected to result in limited mold life. Of the prior art known, only Kayaki provides a system having more than one (two) undercut elements associated with each window, and his invention is further limited in terms of potential hook density and hook orientation by a geometry incorporating singular width rows and columns
Thus it can be seen by examination of the prior art that there is room for significant improvement in the field. Integrally molded fasteners of both the hook-and-loop and mushroom types which can be manufactured by an improved method would be useful. Inexpensive surface fasteners with greater material efficiency would be beneficial. Fastening elements of diverse designs with precise details which can be economically manufactured without limitation by mold removal requirements is desirable. Fasteners with minimal profile thickness would have great utility. Double-sided fasteners and fastener strips with multiple fastening zones have many potential applications. Improved methods for economically assembling products and components are needed. Other applications for improved surface fasteners will be seen throughout this disclosure.
Regarding Self-attaching Systems:
Fastening systems which include hermaphroditic arrays of interengaging mushroom-like structures are relatively well known, such as the system marketed by 3M Corporation as Dual-Lock®. Generally, these systems include relatively flexible stems with overhanging end portions connected to a sheet-form base arrayed in patterns designed to restrict shear as in the examples noted above. Other examples of interdigitating fasteners associated with a sheet form base include: Fox et al U.S. Pat. No. 3,101,517; Ausnit U.S. Pat. No. 3,325,084; McMillan U.S. Pat. No. 3,899,805; Batrell U.S. Pat. No. 4,946,527; Gershenson U.S. Pat. No. 5,097,570; McGanty U.S. Pat. No. 5,212,855; Rouser U.S. Pat. No. 5,634,245; and Davis, U.S. Pat. No. 6,179,625 B.
Gershenson, et al U.S. Pat. No. 5,799,378 discloses a fastening system comprised of two like plates of intersecting walls with bulbous heads on stems at the intersections of the walls for engaging with the generally steeply sloped lower sidewalls of complementary such heads. When engaged, the heads effectively bypass one another by a distance equal to the effective length of their stems, and the walls include stepped segments to accommodate complementary wall segments. The structure appears to comprise generally rigid portions for fastening rigid components and it can be appreciated that even relatively slight flexure of either portion would tend to cause disengagement as the sloped lower sidewalls are caused to bypass. Boe U.S. Pat. No. 5,987,706 discloses a coupling apparatus comprising a plurality of spaced apart apertures with projections positioned on the intervening structure for engaging with like apertures, apparently retained by longitudinal tension when the portions are wrapped around a bundle. Recently, Demarest U.S. Pat. No. 7,036,190B2 discloses a device comprising low-profile flexible interdigitating portions with members retained in engagement within alternately sloped chambers. His disclosure points to the desirability of providing flexible closures for certain types of apparel.